tf.reshape vs tf.contrib.layers.flatten

So I am running a CNN for a classification problem. I have 3 conv layers with 3 pooling layers. P3 is the output of the last pooling layer, whose dimensions are: [Batch_size, 4, 12, 48]_, and I want to flatten that matrix into a [Batch_size, 2304] size matrix, being 2304 = 4*12*48. I had been working with "Option A" (see below) for a while, but one day I wanted to try out "Option B", which would theoretically give me the same result. However, it did not. I have cheked the following thread before